When power is removed from an electronic device, such as a Flash memory module other forms of retention modules, voltages at one or more points in the device can remain at an undesirable level which can result in an unpredictable behavior or states. For example, in the case of a Flash memory module, a voltage can remain on the supply line (e.g., the VDD input line) after power is no longer being actively supplied from outside of the device. Voltage drops with leakage or active current to an undesirable voltage can result when the voltage falls near or below the threshold voltage (Vth) for operating gates of transistors in the module (e.g., about 700-900 mV for some CMOS transistors used in 3.3 V logic gates), where transistor operating behavior is not well guaranteed. This may leave no way to maintain a defined state in an electronic device. The problem may become more severe as devices have very low leakage near Vth of the transistors and thus the undefined state can remain on any electronic device for a very long time. In a periodic environmental monitoring system application, it may happen that device wakes again before supply is completely discharged and it may find itself in one of those undefined state.
One potential solution is to use an off-chip controller to connect the supply line to ground after power is disconnected. However, this requires an off-chip controller to properly connect the supply line to ground every time power is disconnected. Not only does this require an extra step when using the chip, but this too could fail if power is suddenly lost by the off-chip controller.